236 A MANUAL OF ANATOMY. 



area corresponds to the base of the central lobe of the 

 brain. 



The claustrum is connected to the corpus striatum (len- 

 ticular nucleus) at its inferior margin, where the external 

 capsule is wanting, also to the amygdaloid nucleus. 



The amygdaloid nucleus (Figs. 37, 46, 51) is an oval, 

 gray mass continuous with the cortex of the apex of the 

 temporal lobe. It produces a bulging into the anterior part 

 of the descending horn of the lateral ventricle. It is con- 

 tinuous with the claustrum, is immediately under the len- 

 ticular nucleus, and has terminating in it the tail of the 

 caudate nucleus, the taenia semicircularis, also fibres from 

 the external root of the olfactory nerve tract and from the 

 anterior commissure. 



The tsenia semicircularis (one on each side, Figs. 30, 

 46), is a round bundle of white fibres which starts from the 

 anterior pillar of the fornix, passes outward and backward 

 along the inner border of the body and tail of the caudate 

 nucleus, between this nucleus and the optic thalamus, then 

 on into the descending horn of the ventricle, forming the 

 inner part of its roof, to terminate in the amygdaloid nucleus 

 with the tail of the caudate nucleus. 



The anterior commissure can not be shown for its en- 

 tire length in any one section, as it takes a curved course. 

 The dissection in Fig. 34 (see also Figs. 37, 39, 43, 50) 

 shows the commissure. It is a round bundle of white 

 fibres (about an eighth of an inch in diameter) which crosses 

 the anterior part of the third ventricle in front of the ante- 

 rior pillars of the fornix, between which it can be seen from 

 the third ventricle ; its course is then downward and back- 

 ward beneath the lenticular nucleus to terminate in the sub- 

 stance of the temporal lobe at the anterior part of the 

 roof of the descending horn of the lateral ventricle, and 



